You might have abnormal buildup of fluid in the ankles, feet, and legs which is called peripheral edema.
Here are some of the possible causes:
prolonged standing or sitting, especially in a very warm environment, can cause excess fluid to accumulate in the feet, ankles and lower legs. Swelling of the feet is quite a common experience for people on long-haul flights
if the valves in leg veins become inefficient, the return of blood to the heart becomes less effective and blood and fluid accumulate in the feet and legs
severe chronic lung diseases such as emphysema and bronchitis increase the pressure in the pulmonary blood vessels that lead from the heart to the lungs. This pressure acts back on the right side of the heart and the veins returning blood to it, causing swelling in the legs and feet
if the heart is no longer pumping efficiently, fluid builds up in the lungs and other parts of the body, particularly the feet and ankles. This is called congestive heart failure
if protein levels in the blood become low, perhaps because of a poor diet, liver disease or kidney disease, oedema can develop. The proteins in the blood, for example albumen, help to draw fluid back from the tissues into the blood.
Have you recently had a foot or leg wound? Do you have any other symptoms?